This invention relates to anti terrorist barriers capable of stopping the movement of vehicles unauthorized to enter through a trafficway. A vehicle moving toward such a barrier has a certain kinetic energy which is a measure of the hitting power is possesses. This kinetic energy is calculated from the vehicle weight and velocity, and upon impact with such a barrier the kinetic energy is then converted into heat, sound and deformation of the vehicle, and with this invention in deformation also of the barrier. In actual practice, the total energy of dissipation depends upon varying factors prevailing at the moment of impact, all of which need not be detailed here. However, for example, a vehicle moving at 50 mph has five times as much kinetic energy as it would moving at 10 mph; or for example an armored car weighing thirty times as much as a small passenger car and moving at 10 mph would have less kinetic energy than said passenger care moving at 60 mph. The stopping capacity of the barrier herein disclosed is designed, for example, to stop a 10,000 pound vehicle impacting at 27 mph, or a 6,000 pound vehicle impacting at 34.5 mph, it being a general object of this invention to provide a yielding barrier, characterized by a hidden cable within a beam retractably extending visibly across a trafficway.
This barrier is a semaphore type arm in the form of a visible beam that extends across a trafficway, between anchor blocks to which it is attached in closed and effective position. In the open ineffective position the beam is detached from one block and extends away from the other block. Accordingly, the two blocks are at opposite sides of the trafficway, it being an object of this invention to tie these two blocks together, in the effective position, by means of the beam and in a manner which is inseparable. In practice, therefore, the beam is characterized by a flexible cable of substantial strength which yields to vehicle impact dependent upon the magnitude of kinetic energy applied. Upon slight impact the cable yields very little. However, upon great impact the cable yields a substantial amount and flexibly conforms to the vehicle configuration while arresting its motion. The cable then becomes a snare attached to spaced anchor blocks, each in the form of a bollard or the like.
It is an object of this invention to provide a beam support for the aforesaid cable, by which it is retractably carried to fasten between the two anchor blocks. The beam is tubular, so to enclose and hide the cable, and it is adjustable as to length so as to accommodate the distance between the two anchor blocks. In practice, there is an extension tube that is expendable and which telescopes into a yoke tube that is swiveled so as to swing away from a transverse position. The extension tube is initially straight and carries the thimbled end of the cable into alignment with an anchor block to which it is detacheable.
It is an object of this invention to provide means that pivots the cable anchor beam at a first side of the trafficway, to swing away from a transverse effective position. It is also an object of this invention to provide means that swivels the cable carrying beam at a first side of the trafficway, to rotate in a horizontal plane during vehicle impact. In practice, parts of this mounting, at what will be termed the pivot block, are frangible so as to permit horizontal rotation.
It is another object of this invention to provide means that anchors the cable and beam at a second side of the trafficway, to rotate in a horizontal plane during vehicle impact. In practice, the cable end is positioned by the beam to engage over a bit onto which it is latched, and preferably padlocked.
It is still another object of this invention to provide counterbalancing of the beam and cable, with spring compensation of movement to and from a normal horizontal position and a raised position of the beam and cable, where they are arrested.